Percutaneous aortic valves, such as those available from Edwards Lifesciences LLC (Irvine, Calif.) under the tradename SAPIEN® typically utilize an expandable frame having valve leaflets attached thereto. This expandable frame essentially comprises a stent, with the valve leaflets (preferably in the form of tissue membrane) attached to a portion thereof. For this reason, these percutaneous aortic valves are commonly referred to as “stent-valves”. Typically, the percutaneous aortic stent-valve is compressed down upon a deflated balloon catheter, the combined assembly is then inserted into the femoral artery through a covering sheath, and then the combined assembly is delivered endoluminally through the iliac artery and aorta to the valve seat. At the valve seat, the balloon is used to expand the stent so that the stent-valve is set at the valve seat, then the balloon is deflated, and finally the balloon catheter is withdrawn, whereupon the leaflets of the stent-valve act in place of the natural leaflets of the diseased aortic valve.
Percutaneous heart valves of the sort described above currently show great promise, particularly for elderly and/or otherwise infirm patients who cannot tolerate the trauma of conventional open heart valve replacement procedures.
Unfortunately, current percutaneous heart valve systems require the use of relatively large delivery/deployment apparatus. More particularly, since the internal balloon must be capable of expanding the stent portion of the stent-valve to the full size of the natural valve seat, and since the deflated size of a balloon having this full-expansion capability is relatively large, and since the stent-valve must be disposed circumferentially outboard of the balloon, the overall size of the delivery/deployment apparatus is necessarily large. By way of example but not limitation, the Edwards SAPIEN® delivery/deployment apparatus is typically approximately 7 to 8 mm in diameter.
Clinically, this can present a significant problem for the surgeon, since the preferred access to the vascular system of the patient is via the femoral artery, with subsequent delivery to the aortic valve seat via the iliac artery and aorta. However, the femoral artery is typically only about 5 to 8 mm in diameter, and this 5-8 mm range is for the general population as a whole—elderly female patients, who are expected to make up a substantial percentage of the candidate population for percutaneous aortic valve replacement, are on the smaller end of this range (e.g., perhaps 5-6 mm in diameter). Thus, it can be difficult or even impossible to pass the 7-8 mm (diameter) SAPIEN® device through the 5-6 mm (diameter) femoral artery of an elderly female patient, particularly where the femoral artery is tortuous, stenotic and/or occluded. Surgical incision has sometimes been required in order to gain access to a higher level of the ilio-femoral artery (e.g., within the pelvis) that is large enough to accommodate the stent-valve assembly. However, this approach is generally more invasive, and often leads to complications such as substantial bleeding and artery obstruction.
Referring now to FIG. 1, a schematic side view of a catheter-deliverable device, or stent-valve, known in the prior art is shown. Accordingly, FIG. 1 illustrates a schematic longitudinal cross-sectional view of catheter-deliverable device frame 10. The stent-valve may have an expanded diameter of approximately 25 mm. That is, the diameter D of external frame of deliverable device as fabricated and ready for mounting, is for example, 25 mm. However, the stent-valve can be compressed to approximately 4 mm in diameter. Accordingly, the dashed arrows of FIG. 1 show the device mechanically compressed 14 in mounting onto a catheter. The minimum achievable diameter Dmin of the fully compressed device (as limited by device mechanics and geometry) is, for example, 12 Fr (4 mm). FIG. 2 is a schematic longitudinal cross-sectional view of a typical large-diameter delivery balloon catheter (inflatable to diameter 25 mm) shown in a deflated state, e.g. 12 Fr (4 mm). As shown in FIG. 2, to achieve expansion of the stent-valve, it may be mounted on a typical prior art large-diameter delivery balloon catheter that is inflatable to a diameter of 25 mm. Accordingly, in FIG. 2 a shaft or balloon catheter 20 is shown (inflation lumen is omitted for clarity) having guide wire lumen 22. The balloon catheter further includes a compacted material of the deflated balloon 24. Compression of device 10 and reduction of its diameter is limited by size of the underlying catheter upon which it is mounted. The combined diameter, for example, 18 Fr (6 mm) of the device 10 mounted on balloon catheter 20 remains greater than minimum achievable diameter of device alone, for example 12 Fr (4 mm). However, the combined diameter of the stent-valve mounted on to the large-diameter delivery balloon catheter is perhaps 18 Fr or 6 mm, which is too large to insert into some patient's femoral artery.
For the foregoing reasons, there is a substantial need for a new and improved method and apparatus for the endoluminal delivery of intravascular devices to a site within the body.